The peculiar source XSS J12270-4859: a LMXB detected by FERMI ?

TL;DR

This paper investigates the peculiar X-ray source XSS J12270-4859, exploring its unusual variability and potential link to a high-energy gamma-ray source, proposing it may be a microquasar or pulsar, with new XMM-Newton observations supporting its complex behavior.

Contribution

The study provides new high-time resolution XMM-Newton data confirming flaring and dipping behavior, and discusses the source's possible nature as a microquasar or pulsar, linking it to gamma-ray emissions.

Findings

Confirmed flaring and dipping behavior in X-ray observations.

Provided upper limits on fast X-ray pulsations.

Suggested possible association with a microquasar or pulsar.

Abstract

The X-ray source XSS J12270-4859 has been first suggested to be a magnetic cataclysmic variable of Intermediate Polar type on the basis of its optical spectrum and a possible 860 s X-ray periodicity. However further X-ray observations by the Suzaku and XMM-Newton satellites did not confirm this periodicity but show a very peculiar variability, including moderate repetitive flares and numerous absorption dips. These characteristics together with a suspected 4.3 h orbital period would suggest a possible link with the so- called "dipping sources", a sub-class of Low-Mass X-ray Binaries (LMXB). Based on the released FERMI catalogues, the source was also found coincident with a very high energy (0.1-300 GeV) VHE source 2FGL J1227.7-4853. The good positional coincidence, together with the lack of any other bright X-ray sources in the field, makes this identification highly probable. However, none of the other standard LMXBs have been so far detected by FERMI. Most galactic VHE sources are associated with rotation-powered pulsars. We present here new results obtained from a 30 ksec high-time resolution XMM observations in January 2011 that confirm the flaring-dipping behaviour and provide upper limits on fast X-ray pulsations. We discuss the possible association of the source with either a microquasar or an accreting rotation powered pulsar.